The biochemical and biological properties of hamster cells transformed by equine herpesviruses (EHV) types 1,2, and 3 will be studied. The structure of the viral genome of each virus will be elucidated by restriction enzyme mapping methods and the shared DNA sequences will be identified. These findings will be used in blot hybridization assays of transformed and tumor cells to identify which viral DNA sequences are present and are expressed in herpesvirus oncogenesis. The viral products expressed in these cells will be identified and specific DNA fragments will be tested for biological activities. In addition, the structure of the DNA of defective interfering (DI) particles of EHV-1 will be mapped and the biological properties of D1 particles will be investigated, with emphasis on the capacity of these particles to mediate persistent infection and/or transformation of mammalian cells.